Georgia CDL — Air Brakes Practice Test 9

1.Why are the parking and emergency brakes on a truck or bus kept applied by mechanical force rather than by air pressure?

Air pressure can gradually leak awayMechanical force always stops the vehicle in a shorter distanceAir pressure is too strong and would damage the drumsMechanical parts never need to be inspected

2.You are testing a combination vehicle with the brake pedal held fully applied and the engine off. What is the maximum acceptable rate of air loss?

Less than 2 psi per minuteLess than 8 psi per minuteLess than 1 psi per minuteLess than 4 psi per minute

3.You always drive a straight truck whose antilock system is working on every axle. In a genuine emergency stop, this permits you to:

Push the brake pedal all the way to the floorCount on a shorter stop than the same truck would make without the systemRelease and re-apply the pedal every time you feel a wheel lockReach for the parking brake control instead of using the pedal

4.The correct rhythm for snub braking on a long downgrade is to:

Hold light, steady pedal pressure the entire way downBrake hard for one second out of every five, regardless of speedSlow about 5 mph below your safe speed, release, then reapply when back at safe speedUse the parking brake knob in short pulls to save the service brakes

5.How does a "Z" restriction differ from an "L" restriction on a CDL?

Z applies only to school bus drivers, while L applies to all CDL holdersZ limits night driving, while L limits interstate drivingZ bars CMVs with full air brakes, while L bars CMVs with any air brakesZ and L are identical; states simply use different letters

6.A safety relief valve on an air tank is normally set to open at about 150 psi. If this valve releases air, what does that tell you?

Something in the system is out of order and needs repair by a mechanicThe tanks are fully charged and the system is working normallyThe alcohol evaporator needs to be refilledThe spring brakes have just been released

7.With the engine at operating rpm and a dual air brake system, how quickly should tank pressure climb from 85 psi to 100 psi?

Within 45 secondsWithin 2 minutesWithin 3 minutesWithin 10 seconds

8.For a normal stop in an air-braked vehicle, the manual says to press the brake pedal so that:

The vehicle comes to a smooth, safe stopThe wheels lock briefly to prove the brakes workThe application gauge always reads maximum pressureThe spring brakes pop out just as you stop

9.What is the main cause of brake fade on a long downgrade?

Excessive heat from using the brakes too much instead of engine brakingMoisture in the air tanks reaching the brake chambersThe governor cutting out at too low a pressureCold drums gripping the linings too tightly

10.While driving, the low air pressure warning buzzer suddenly sounds. Your best response is to:

Keep driving to the next truck stop and have it checked thereStop and safely park as soon as you can, while braking is still controllableShift to neutral and coast so the compressor can catch upSpeed up so the compressor turns faster and rebuilds pressure